*edit: image was not visible in first post
I am new to ggmap. I am trying to plot specific points from grids on to a map, but I only have the gps coordinates for the corners of the grids. Is there a way to build a 10 X 10 grid between these points, extract the center of the squares in those grids, and plot a subset of those points?
here is what my map looks like now, with the four corners of three different grids. I would prefer not to include code, as it contains location data.

I am not sure how to go about this, or if it is even possible.